Summary: This project proposes to study neutralizing antibody responses to the two major infectious forms of vaccinia virus, the intracellular mature virus (IMV) and the extracellular enveloped virus (EEV). Neutralizing activity in vaccinia immune globulin will be fractionated using proteins and peptides. Reverse genetics will also be used to decipher structure-function relationship in IMV and EEV envelope glycoproteins.